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        The Beginner’s Guide to Measuring Defense

        by Neil Weinberg
        September 5, 2014

        There’s a decent chance you’ve arrived at this page without a serious desire to hear more about defensive statistics. Trust me, I understand your frustration and your fatigue. Defensive stats like Ultimate Zone Rating and Defensive Runs Saved are controversial in some circles because they are reasonably new and the underlying data is somewhat hidden from view. You hear words like “flawed,” “absurd,” and “subjective” surrounding them. You’re tired of it.

        Yet I’d like to lay out why we have advanced defensive statistics and how they work in the abstract. You won’t get to the end of this post and decide that UZR has perfectly measured Alex Gordon’s defense, but hopefully you will have a better appreciation for why we measure defense the way that we do.

        Why Errors and Fielding Percentage Come Up Short

        For decades, the basic measurements of defensive performance were errors and fielding percentage. We used to judge players based on how well they avoided making errors on balls they fielded. If you didn’t kick the ball or let a throw sail wide, you were considered a quality defender. Certainly, those who were able to watch enough games developed a sense about which players were better defenders, but from a statistical standpoint, all we had were errors, assists, and putouts.

        These statistics aren’t very useful, however. You certainly want to avoid errors because in order for something to be called an error you have, by definition, failed to convert a batted ball into an out. Yet there are two key problems with errors. First, they are determined by official scorers who don’t always make the right decision. Human error isn’t a problem, per se, but you’ve all seen enough scoring decisions to be skeptical about the quality of their decision making.

        More importantly, however, is that errors are a subset of misplays. Even if official scorers got the rule book definition exactly right and perfectly uniform, we would still be ignoring a huge portion of bad defensive plays. Think back to a moment when you watched a player get a horrible jump on an easy ball. Think about the time an infielder took too long to get the ball out of their glove. Picture an easy pop fly falling four feet from the second baseman. None of those are errors even though they are relatively easy plays.

        Measuring defense using Assists + Put Outs / Assists + Put Outs + Errors  ignores a huge slice of defense. If a player fails to get to an easy ball, there is no penalty. That alone should be reason enough for you to want something better.

        Turning Batted Balls Into Outs

        So if errors and fielding percentage fail to provide the entire picture of defense, what exactly should we be using? It’s not that errors lack importance, it’s that making an error isn’t the only way to screw up.

        Instead of fielding percentage, the next step forward is something like defensive efficiency or Revised Zone Rating (RZR). Both statistics strive to tell you similar truths; how often a fielder turns batted balls into outs. In other words, we don’t care whether you make an error or if you don’t get to the ball. We care if you made an out or if you didn’t. The distinction between an error and a play not made is arbitrary. If 200 batted balls were hit to the third baseman’s zone during a given period of time, do we care if he made 20 errors and failed to get to 20 balls or if he made 10 errors and failed to get to 30? For the most part, we do not (unless they were horrible throwing errors leading to multiple extra bases). In both cases, he turned 80% of batted balls into outs.

        This is a much better way to measure defense because it captures every play rather than just the subset of plays in which the fielder came in contact with the baseball. However, this type of metric has it’s limitations because it does not control for the difficulty or importance of the play.

        Not All Batted Balls Are Alike

        This is another simple truth about which everyone can agree. A rocket off the bat of Miguel Cabrera and a routine grounder from Seth Smith are very different batted balls. We want a defensive metric that includes all batted balls, but we also recognize that even moving in that direction doesn’t take use far enough.

        Turning 80% of balls in your defensive zone into outs is great, but if a large portion of those are easy plays, that’s much less impressive than if they were more difficult.

        Difficulty

        A screaming line drive up the left center field gap and a routine fly ball to center field are both in the center fielder’s defensive zone. One of those balls is much easier to field than the other, so it stands to reason that more talented defenders would get to the more difficult play more often.

        So we want a defensive statistic that does something to control for how challenging that particular play was to make. You should get more credit for a tough play than for an easy play. Typically, the modern defensive statistics (UZR, DRS, etc) measures this variable by determining how often that play is made by the entire league.

        For example, if a certain play is made 40% of the time, then if the fielder makes the play, he gets credit for 0.6 times the run value of that play (we’ll get to this in a second). Because the average fielder should make that play 40% of the time, by making the play you get credit for the difference.

        The advanced defensive stats all include these percentages based on multiple years of data. So if that screaming line drive is caught 30% of the time by center fielders, we’re basing that on all similar line drives over the last six seasons, for example. Humans have to code where the ball was hit, the approximate elevation, etc, but the algorithm is the one analyzing the data. The human being doesn’t say “that was a 40/60 play,” they say, “that ball was hit to X at about Y speed” and the computer compares it to all other similarly coded plays. There can be measurement error in defensive stats, but we aren’t talking about a random person guessing at the difficulty of the play.

        Run Value

        Using all plays and controlling for their difficulty is important, but we also want to consider how valuable it was to make that play. For example, imagine a hard hit ground ball deep in the hole at short. Maybe one out of every fifteen shortstops are able to turn it into an out. Call it a 7% chance the play gets made. If you make that play, you will get a lot of credit because it was very difficult, but if you hadn’t made the play, how much would it have cost your team?

        In addition to difficulty, we also want to add in the average run value of the batted ball in some way. On that tough ground ball, if the play isn’t made then it’s almost always a clean single. It wouldn’t go for extra bases. No one is scoring from first. The play is hard to make, but the cost of failing to execute is lower than if we’re talking about a ball up the gap. So we want to multiply the difficulty times the value of making the play. You can read all about the specifics of this at our UZR Primer, but the concept should be pretty clear. You want the difficulty times the value of making the play.

        So What Do We Have?

        Instead of errors and fielding percentage, we want a defensive statistic that considers all batted balls and not just times the fielder touches the ball. We want a stat that measures the difficulty and the value of each play. That’s exactly what our advanced defensive metrics do. There’s nothing subjective or subversive going on here.

        We’re taking some very fundamental questions about every play and we’re using multiple years of data to answer them. Limiting the number of errors you make is good, all else equal, but if you can get to 10% more batted balls than someone else while making a couple more errors, you’re almost certainly the better defensive player.

        Limitations

        It’s important to note that this does not mean that defensive stats are perfect. We’re relying on imperfect data. The video scouts can’t perfectly determine the location, velocity, and angle of every batted ball from watching the game tape. They do a very nice job, but there is measurement error. There will always be measurement error.

        Additionally, sample size is an important consideration. There are a pretty small number of difficult batted balls hit to every fielder each year. If you luck into a few good plays or miss a few because you happened to be working with a bum ankle, your rating can fall quickly. That’s not a flaw of measurement, it’s a fact of baseball. You don’t get 700 chances to make dazzling plays each season. Even if we could get our measurements from an omnipotent baseball deity, we couldn’t do anything about sample size.

        The same thing is true with offensive statistics. If a hitter goes 20 for 40 (a .500 batting average), you don’t say that his batting average is wrong. He got those 20 hits. What you might say is that 40 at bats is too small a sample to tell us very much about this hitter even if it is an accurate reflection of those 40 at bats.

        Defensive metrics work the same way with respect to sample size. The metric isn’t wrong just because the output looks too large or small (although it could be wrong), but it might not be a very good reflection of what will happen in the future or how talented the fielder was for the previous few games.

        You don’t need to take the precise measurements as gospel and I wouldn’t recommend it. But you should appreciate what these numbers are trying to tell you. These stats are answering the questions you want to have answered. There are all sorts of ways we might improve the measurements included in these stats and the ways in which we use them to determine talent and performance, but the fundamental logic is exactly what you want.

        You want to know something about every ball hit to a fielder’s zone. You want to know how often that play gets made and if the fielder made it. And you want to know how valuable that play is on average. You don’t care about errors and put outs. You care about outs and things that aren’t outs. Don’t you?

        Have questions about defensive stats? Ask them in the comments!





        Learning to Speak Saber: Runs and Wins
         
        The Beginner’s Guide to Using Statistics Properly

        Neil Weinberg is the Site Educator at FanGraphs and can be found writing enthusiastically about the Detroit Tigers at New English D. Follow and interact with him on Twitter @NeilWeinberg44.

        64 Comments
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        Yirmiyahu
        10 years ago

        With “Run Value”, do the advanced stats take into account baserunners/outs/game state?

        Making an out on your hard-hit ground ball at SS is a lot more valuable when there’s a runner on 3B in a close game, than it is for that same ball with no one on in a blowout.

        Referring to this component as “how valuable it was to make that play” implies that game state is taken into account, but that would mean we’re giving credit for defensive clutchness. We don’t want that. I’m guessing the algorithms just take into account how many bases that type of ball *typically* goes for if it gets through, rather than how valuable the out was in that particular instance?

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Yirmiyahu

        Correct. We are talking about the average value of that batted ball for all situations. Not just that specific one. Outs, runners are not considered.

        2
        Bradsbeard
        10 years ago
        Reply to  Neil Weinberg

        Interesting thought though. There’s no reason why game state couldn’t be factored to arrive at a defensive WPA, is there?

        1
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Bradsbeard

        This could theoretically be done, sure. It would just be super volatile for obvious reasons.

        1
        Shirtless Johan Santa
        10 years ago
        Reply to  Neil Weinberg

        It would be a lot of fun to see who has the best defensive WPA or best defensive “clutch”.

        Unless you were Brooks Conrad when he played for Atlanta.

        3
        Dan
        10 years ago

        What is the difference between the Def score in the team fielding page and the Def score that goes into team offensive WAR?

        As an example, the Nationals show 34.3 Def score in the offense section and only 6.6 in the fielding section.

        0
        Yirmiyahu
        10 years ago
        Reply to  Dan

        On the fielding section, they have -4.9 UZR runs, which somehow translates into a +1.1 UZR/150 (this seems like it’s a database error), and +6.6 runs from defense?

        On the batting section, Fielding runs is +3.6, plus 30.7 runs positional adjustment, for a total of 34.3 total runs from Defense.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Dan

        The Def you’re looking at on the main page includes all players on that team. The Def you’re looking at on the team fielding page only includes players who played defense.

        That sounds super weird, but the simple answer is that DH’s aren’t listed in the fielding section because they don’t count as defensive innings. At this point in the season, most AL teams will get -12 or so defensive runs as a result and the NL teams are like +30 because of the whole DH/P thing. This doesn’t show up on the fielding page though because those aren’t innings of actual defense.

        0
        Yirmiyahu
        10 years ago
        Reply to  Neil Weinberg

        But shouldn’t the UZR numbers on the defensive section match up with the fielding numbers on the batting section? The DH thing should only affect the positional adjustment.

        And how can the Nationals and Diamondbacks have a positive UZR for the season, and then have that become a negative UZR when scaled to 150 games?

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Yirmiyahu

        There is no UZR for catchers. We use rSB + RPP. So UZR doesn’t equal fielding runs.

        The scaled to 150 games is based on something called “Defensive Games” not regular games. In other words, it normalizes the number of chances at each position to the 150 game norm. So theoretically, if your worst defender had gotten more chances than normal nad your best defender had far fewer chances than normal, you could observe a switch like this.

        For example:

        A -10 LF with twice as many chances as average would be a -5 UZR/150.

        A +5 CF with half as many chances as average would be a +10 UZR/150.

        So UZR says -5, UZR/150 says +5. It’s never that extreme, but with enough players it could happen

        1
        Yirmiyahu
        10 years ago
        Reply to  Neil Weinberg

        That makes sense. Thanks. Okay, so with the Nationals again…

        -4.9 UZR + 6 rSB + 2.5 RPP = 3.6 raw fielding runs (as seen on the ‘fielding’ column on the batters section).

        And on the defensive page, there’s a +3.0 positional adjustment (probably just to neutralize everything to a league-average 0??), resulting in +6.6 total defensive runs.

        And on the batters section, there’s +30.7 positional adjustment (taking into account the lack of a DH), which results in +34.3 total defensive runs?

        1
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Neil Weinberg

        Looks about right? Sorry I don’t have it open in front of me. But that’s how it should balance out.

        1
        Cody
        10 years ago

        Is there any taking into account defensive shifts? How does that work? Sounds like a managers defensive shifts could severely alter the defensive value of players.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Cody

        If the stringer (guy coding the game) determines that 1) a shift was on and 2) the shift affected the defensive outcome of the play, that play is removed from the data set. Obviously, that shrinks our sample size, but it’s better than guessing (which you might have to do because of camera angles).

        It’s my understanding there is work being done to revamp this for 2015!

        1
        Cody
        10 years ago
        Reply to  Neil Weinberg

        Ok cool, thanks for the response.

        0
        Dennis
        10 years ago
        Reply to  Neil Weinberg

        Doesn’t this penalize teams that employ more pronounced shifts? The O’s use the shift a lot, and while their defensive numbers are great, the value of these plays is being lost to both the fielders and the pitchers.

        1
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Dennis

        Basically just assumes average performance during shifted plays. I wouldn’t call it a penalty as much as a the best we can do without good data on pre-pitch positioning.

        1
        Andy
        10 years ago
        Reply to  Neil Weinberg

        IOW, the equivalent of the IBB on wOBA. It’s not included as a PA, which is the same thing as saying it’s treated as an average PA–i.e., a PA with an average run-creating value.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Neil Weinberg

        Not exactly, because IBB is treated as that player’s average PA while shifts are just assumed to yield totally average performance across the board because we currently don’t have proper data to evaluate them. But I see what you mean.

        0
        Cody
        10 years ago
        Reply to  Cody

        What about defensive positioning as well, sounds like that would matter a lot.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Cody

        Also not really included. Basically, this means that if a guy is very good at positioning, it might show up in his range score rather than in a separate category.

        2
        Yirmiyahu
        10 years ago
        Reply to  Neil Weinberg

        What if a ball is missed because of defensive positioning other than a shift? Say, the infield is playing in at the edge of the grass with a runner on 3B, and a ball gets through the big hole in the middle, or goes just over someone’s head? Or a shallow single against an outfielder playing ‘no dobules’ deep?

        That’s not a ‘shift’, but it’s not the player’s choice to be playing too far in or out. Does that play get thrown out by the stringer, or does the fielder just take the hit on his range score?

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Yirmiyahu

        It’s my understanding the fielder will get docked there. Although I don’t know the technical definition of “Shift” used to determine if the play gets thrown out.

        0
        Yeah
        10 years ago
        Reply to  Yirmiyahu

        That sounds like a system with a lot of serious holes.

        0
        bstar
        10 years ago
        Reply to  Neil Weinberg

        Neil, since a human being is watching all the plays with DRS and then 3 or 4 more people review the entire game with the stringer, couldn’t it be reasonably stated that DRS IS taking starting position into account, although in a non-scientific way?

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  bstar

        I know a little less about DRS than I do about UZR, but I don’t think they take positioning into account because you can’t verify most positioning due to limited camera angles

        0
        BaseballGuy
        10 years ago

        Seems obvious that good fielders help good pitchers, but isn’t it also true that good pitchers (especially those with excellent command) help fielders get better ratings because positioning works better when you know the pitch is going to be in a certain location. Can you tease out that effect?

        1
        AK7007
        10 years ago
        Reply to  BaseballGuy

        It’s counterintuitive, but Jeff looked a bit at this phenomenon awhile back. The Rays had the full lefty shift going in the infield, outfielders positioned normally, and pitches going to the outside third. They must be crazy right? When he looked at the numbers, it turns out that hitting a ball on the ground to the opposite field is very unlikely, even for pitches over the outer third. The batted ball profile on pitches to the outer third does change for balls hit in the air though. Positioning is more about knowing your own range limitations and the batted ball tendencies of the batter in the box, but not as much about where the pitcher is throwing. There might be some effect, but it’s not as big as those other factors.

        1
        jim fetterolf
        10 years ago
        Reply to  BaseballGuy

        Been suggesting this for awhile, Pitching Independent Fielding, PIF. Fielders are positioned and leaning for a specific pitch in a specific spot to a specific hitter. If the pitcher misses the defender is out of position.

        0
        Dennis
        10 years ago

        Couple questions:

        1: Who gets credit forruns saved due to a shift?
        2: how is credit assigned on HR saving catches?

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Dennis

        1) No one right now. Shift plays are excluded from UZR/DRS. In theory, credit is determined the same way as long as you know where everyone started.

        2) HR robbery would work just like normal. Average ball hit to location X would be worth like 2.2 runs or something (estimating) and the play would be rarely made so there’s a lot of credit (maybe 80 or 90 percent) to the defender.

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        MGL
        10 years ago
        Reply to  Neil Weinberg

        BIS uses GFP and BFP (good and bad fielding plays) to credit fielders with robbing home runs. I do not know if they are included in DRS. I don’t think so. I think they are in a separate category.

        With UZR, if an outfielder robs a HR he is only going to get credit for making an out on a deep fly ball which is probably going to be only some small percentage of a run, depending on how deep and where in the OF the ball was. The data that UZR uses does not include whether a ball was “over the wall” or even where the wall was as compared to the ball, although to some extent that can be calculated I suppose (although UZR does not do anything with respect to walls).

        And the “zones” that UZR uses are not that small. They are like maybe 20 feet by 20 feet in order to get decent sample sizes in each bucket. So a ball caught over the wall would be in the some bucket and be treated the same as a ball in the same general location but 10 feet shallower, for example.

        You might think, and you would be right, that you could come up with an algorithm that gives more credit if a ball, for example, is 3 feet deeper than another ball, without using separate buckets (which would destroy the sample sizes), using something like a LOESS regression or smoothing function. Shane Jensen’s SAFE system does that. UZR, unfortunately, does not, at the present time. Maybe in the future it will.

        1
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  MGL

        Thanks for the clarification. Good info!

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        Andy
        10 years ago
        Reply to  MGL

        Yes, thanks for this. I have been speculating that with all these video data, it’s only a matter of time before buckets are replaced with a continuous function. In fact, it seems to me that what we mainly need is the speed of the ball off the bat and the angle of its trajectory, though I suppose spin matters, too. But eventually, we should be able to dispense with the human judgment entirely.

        0
        pft
        10 years ago

        When are we going to get play by play, game logs and H-A splits for defensive metrics. Without these we as fans can not validate them and their use seems more a matter of faith than anything else.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  pft

        From a practical perspective, BIS makes their profits from selling their data. So releasing everything they have isn’t really in their interest. And would that prove anything? I assume you don’t think they’re lying about how they do the calculations, so all you would care about is how the ball is coded in. There’s no reason to think they’re doing a horrible job or anything.

        What would play-by-play let you do that would satisfy you?

        1
        BenRevereDoesSteroids
        10 years ago
        Reply to  Neil Weinberg

        “There’s no reason to think they’re doing a horrible job or anything.”

        That is kind of the point. It is a matter of faith. It would be nice to have, at the very least, someone else take a look at it and give some (public) feedback. But as it stands now, we don’t know what to think.

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        BenRevereDoesSteroids
        10 years ago

        Glad to see a nice new primer on defensive stats, but…

        “For example, if a certain play is made 40% of the time, then if the fielder makes the play, he gets credit for 0.6 times the run value of that play (we’ll get to this in a second). Because the average fielder should make that play 40% of the time, by making the play you get credit for the difference.”

        That part actually seems a little odd to me. Never actually knew that was part of it. Wouldn’t “Difficulty x Value” be akin to giving an extra boost to a hitter’s wOBA because his home run happen to come off Kershaw? Are there versions of UZR where you can just look at the Value or just a Difficulty average? Or am I just not grasping something?

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  BenRevereDoesSteroids

        I think you’re not grasping something.

        Let’s use an example.

        A fly ball way over the head of the CF. Let’s assume that given the park/other conditions, this type of batted ball is fielded by a center fielder about 30% of the time (making this number up).

        So if you are able to make that play, you get credit for 70% of the difference between the average run value of a hit in that location minus the value of an average fly out. So let’s call those 0.5 and -.25 runs (making these up). So the value of making that play is 0.75 runs and you get credit for 70% of that play because that’s the difference between you and the average fielder. So you would get 0.53 runs added to your UZR (or whatever).

        Does that make sense?

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        Nivra
        10 years ago
        Reply to  Neil Weinberg

        I’m not sure I agree with this methodology. This means we would see an increase in UZR if a fielder shifts over from a standard fielding position to an off-set fielding position, doesn’t it?

        Let’s say a CF shades towards the right CF gap, and gives up on plays to the left CF gap. On balls hit to left-center-center, the average CF has a 50% chance of making the play, and on balls hit to right-center the average CF has a 10% chance of making the play. This fielder shifts over so the 50% left-center-center chance moves down to 10%, and the 10% right-center moves up to 50%.

        That means he would miss 40% of plays to left-center-center, and make an additional 40% of plays to right-center. But the run-value of plays to left-center-center, since the average is 50%, is worth almost half as much as the run-value of plays made to right-center.

        So eventhough his range is identical, by shifting over to cover the “higher UZR value plays” and giving up the “lower UZR value plays,” his overall UZR goes up.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Nivra

        Two points. One being that the current methodology basically says positioning is part of your range. When you think about it, there’s no reason why that’s a problem. It’s just less precise than we would prefer to be. If you chose to shade in one direction, you’re either helping or hurting yourself.

        The other is that we simply don’t have pre-pitch fielder location because of the camera angles available. That may changes as early as next year.

        0
        Bradsbeard
        10 years ago
        Reply to  Neil Weinberg

        Right. To the extent a fielder positions himself in a way that he can “easily” make a catch on a low-probability ball, he has to abandon ground by which he could have fielded a ball the opposite way. So he could be playing very poor defense or very good defense depending on the outcome. But as I understand it, the outcome is all we’re really concerned about here. Over a large sample, that kind of positioning should punish him. But if he’s constantly positioning himself perfectly, he deserves credit for the outcome regardless.

        The same thing occurs in pitching or hitting. Pitchers may get by with a hanging curve that gets popped up and still. Get credit for the out. But if he keeps throwing it there, his value will drop over a large sample. A batter may sit fastball and run into a few of them until pitchers learn to throw off-speed to him. But until they do, over a small sample this hitter may post some absurd numbers.

        0
        Deelron
        10 years ago

        Liked the article, I’m definitely going to use “absurb” more often, it’s like absurd but it just has something else that makes it special.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Deelron

        Thanks for the catch.

        0
        joser
        10 years ago
        Reply to  Deelron

        As an urban guy, I find the asurbs are all around the edges of town.

        2
        Jdank
        10 years ago

        Thanks for all this info. Here’s the question. How is an OF credited for cutting off a ball, cleanly hit into a gap or corner and holding the runner to first? Since there a hit, there’s no out recorded, but this defense has a huge impact on base runner position and subsequent plays. Thanks!

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Jdank

        I’m not sure which bucket it falls into (arm or range), but the basic calculation works the same way. You have the value of cutting off the ball and how often similar batted balls are cut off on average.

        0
        Andy
        10 years ago
        Reply to  Jdank

        Don’t know if they do this, but they could just provide a run value for a ball hit in that area. E.g., if the ball is not cut off, it’s a double, which has a known run value greater than that of a single–about 0.30 run, I believe. Or there might be assigned a small probability that a ball not cut off would be a triple, which has a greater run value. One might determine a weighted value, based on the relative probabilities of a double or a triple resulting from a ball not cut off. So maybe somewhere between 0.30 – 0.40 run.

        Then one determines from the historical data how often a fielder cuts off that ball. If it is 40% of the time, a fielder cutting off the ball gets credit for 60% of the run value, so let’s say, 0.18 – 0.24 run.

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        Emmett
        10 years ago

        Does UZR account for bases saved on plays, even if an out isn’t recorded. Say a runner is on second and a hard ground ball is hit to the hole. Adrelton Simmons dives to stop the ball that only 15% of fielders get to, but doesn’t have time to get the runner at first. However, he stopped the runner on second from going home? Or when an outfielder cuts off the ball in the gap to hold a runner to a single? It seems like there is value here that might not be accounted for.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Emmett

        Yes, defensive metrics do this. Usually this winds up in the “arm” section of a metric. But you will get credit for preventing runners from advancing. But remember, everything is build around average. I can’t speak to the exact way UZR and DRS do this differently (if at all), but they incorporate this kind of thing.

        0
        bstar
        10 years ago
        Reply to  Emmett

        Emmett, I’m pretty sure DRS’s +/- system also functions as a sort of grab-bag to reward great plays that might fall through the cracks of what they are normally measuring.

        Andrelton made a play last year by tagging out a would-be basestealer by reaching in between his legs to make the tag. I recall DRS using this as an example of a great play that they will reward.

        Of course, he got the out on that one. So I don’t know about plays where an out wasn’t recorded.

        0
        Charles Mann
        10 years ago

        Once Field FX and TrackMan A/S has more data, will the various groups be able to refine their defensive measurements? It seems that data from the tracking services will be more objective than a stringer’s subjective opinion on how “hard” a particular play might have been.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Charles Mann

        Yes. Assuming the data looks like what we’ve been shown, it should allow us to remove most of the measurement error involved in these stats. Won’t fix the sample size, but nothing will fix sample size issues because they are simply a fact of the game.

        0
        Bpdelia
        10 years ago

        I use the defensive metrics but they obviously are not perfect.

        The effect of good range fielders next to each other is a serious problem (for instance Ellsbury and Gardner,Dyson and Gordon, etc.) but more importantly i don’t like that the adjustment is calculated with respect to the average fielder at a position. Gordon and Gardner should not be measured against only left fielders. It skews the averages too much.

        I’d feel much more comfortable if the positional adjustment was simply OF, middle infield, corner infield.

        Gardner shouldn’t look like a world beater because the Yankees happen to have a better defender on the team. He shouldn’t be compared with Carlos Quentin and the like

        I think the stat would be much more useful if each defender was compared to a much larger group.

        Also, no evidence, but the issue many seem to have is the WIN total being assigned to defense.

        In his best years the fact that carl Crawford was worth three or four wins on defense alone was very difficult to believe.

        Sometimes when data disagrees with conventional wisdom or common sense so drastically we need to closely examine if we’ve measured properly.

        Otherwise we are just replacing one form of dogmatic belief with another.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Bpdelia

        There’s a big gap between corner outfielders and center fielders defensively and between SS and 2B, and 1B and 3B, so I’m not sure why your proposed changes would be a good idea or useful.

        I do think there’s something to the notion that having an insanely good fielder next to you could alter your rating because if they gobbled up enough plays that you should have fielder 10% of the time that most CF wouldn’t have, you could get a little boost.

        But moving Gardner to left because they have someone better isn’t a real problem because the positional adjustment accounts for the boost he gets rating-wise. Perhaps we could refine the adjustment a little, but that’s what it’s for.

        0
        Bpdelia
        10 years ago
        Reply to  Neil Weinberg

        What I’m saying is i don’t think the idea of the positional adjustment does any good

        Simply drop all fielders into a bin with raw balls into out numbers. Don’t compare them to average fielders. It doesn’t give a stable or even useful barometer.

        We can then see who has the highest rating of turning balls into outs and just group them by position if we want to sort.

        I don’t understand why extra credit should be given to Alex Gordon for not being able to play defense well enough to be in center field. It feels wrong.

        Rate all fielders on what they do to balls in their zone. Period. No adjustment is needed.

        We all know it’s harder to play center field than left. On uzr and def war leaderboards Alex Gordon should be beneath just about every center fielder in the game.

        Because they are better fielders than him. He should not be deriving more wins from his defense than any center fielder in baseball. Because they are better fielders than he is.

        The adjustment isn’t needed, doesn’t really make sense and skews rankings and war totals based on things completely out of a players control.

        The fact that in any one season two american league teams may need to squeeze a dh type into left field doesn’t make Alex Gordon any better at all. So why should the measurement of how many wins he produces go up based upon how other teams are aligning their outfields?

        Also while everyone knows it’s “wins above replacement” for all intents and purposes it sits in the mind as “player x was worth x amount of wins”. The replacement level for left fielders isn’t just left fielders. It’s out fielders. Especially since replacement defense first players are all over the minor leagues.

        The adjustment gives the impression that Alex Gordon, or Gardner, or 2009 Crawford are so amazing that they are some of the best defenders in baseball. When of course they quite simply aren’t. Perhaps Gardner. But a guy who cannot play center field is obviously LESS valuable and wind LESS games than every single cf, ss, 2b and many 3b in baseball.

        You shouldn’t get a bonus for being the best at a bat first position. Your individual contributions should not get a boost because other left fielders stink. Certainly not to the point of appearing to be better than almost every other defender in the game.

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Bpdelia

        You’re actually arguing for a less accurate defensive statistic because you think this one isn’t accurate enough. Different positions are asked to field different numbers of balls of different difficult.

        The positional adjustment counter-acts that we use defensive stats compared to league average. We compare them to league average at that position because *it’s the only thing we can compare them to.* You can’t compare a CF and a LF because they are fielding different types of batted balls. Same is true for 3B and SS for example.

        It’s perfectly fair to say there might be a better way to do the positional adjustment, but your solution, as I read it (and I’m sorry if I’m misunderstanding) is to make the stat less helpful.

        0
        magick sam
        10 years ago

        what does seth smith have to do to avoid being used as an illustration of futility?

        0
        Bpdelia
        10 years ago
        Reply to  magick sam

        Have a less alliterative name?

        0
        random internet dude
        10 years ago

        It used to be that UZR fielding %s were based on your position only, so if you had pop fly that the SS gets 90% of the time and the 2B gets 10% of the time (but is gotten 100% of the time) and the 2B gets the ball, then he gets the credit like he made a really difficult play when, in fact, he just made a routine play. Has that been fixed yet?

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  random internet dude

        I don’t know about this specifically, but this is counter-acted by the fact that the run value of that play would be tiny. Can’t speak to if changes have been made on this, though. Better question for MGL.

        0
        FIP'n good
        10 years ago

        Awesome thanks!!!!!!!

        0
        Mike Pozar
        10 years ago

        Is a middle infielder’s ability to turn double plays measured specifically?

        0
        Neil WeinbergMember since 2020
        10 years ago
        Reply to  Mike Pozar

        Yes. rGDP or DPR depending on if you like DRS or UZR.

        0
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